Method and apparatus for cementing underwater wells



1962 J. A. HAEBER ETAL 3,050,117

METHOD AND APPARATUS FOR CEMENTING UNDERWATER WELLS Filed Oct. 25, 1959 2 Sheets-Sheet l INVENTORSI J. A. HAEBER N. B. NEWMAN L. G. OTTEMAN mx THEIR AGENT 2 Sheets-Sheet 2 Aug. 21, 1962 J. A. HAEBER ETAL METHOD AND APPARATUS FOR CEMENTING UNDERWATER WELLS Filed Oct. 23, 1959 3,056,117 Patented Aug. 21, 1962 METHOD AND APPARATUS FOR CEMENTING UNDERWATER WELLS John A. Haeber, Nicholas B. Newman, and Lloyd G.

Otteman, Houston, Tex., assignors to Shell Oil Company, a corporation of Delaware Filed Oct. 23, 1959, Ser. No. 848,283 9 Claims. (Cl. 16621) This invention relates to the cementing of offshore wells and pertains more particularly to a method and apparatus for cementing wells from a floating vessel positioned over an oflshore well wherein the wellhead assembly is positioned entirely under water, preferably on the ocean floor.

Many problems are encountered in the cementing of wells drilled at offshore locations, especially where the well is drilled from a floating vessel with the wellhead positioned under Water. In general, the equipment positioned at the top of the well, often known as a Wellhead assembly or a casinghead, constitutes a casing suspension body through which one or more strings of casing extend and depend therefrom. Originally, the wellhead assembly is mounted on the top of a conductor pipe which may be sunk several hundred feet into an ocean floor. Thereafter, after drilling has progressed, one and usually more strings of well casing are inserted through the wellhead assembly and conductor pipe and are cemented in place, the top of each casing string being hung from the Wellhead assembly by means of a casing hanger.

At the time casing cementing operations are carried out, the well is full of fluid, either drilling fluid or seawater. It is necessary that this fluid in the Well be allowed to flow out of the Well. It is a general practice to displace it out of the well as cement is pumped down a cementing string, through the casing string and up the annular space between the outer wall of the casing string and the wall of the borehole. When additional strings of casing are inserted and cemented in place, the cement is pumped down the innermost casing string while the fluid in the well is displaced ahead of it and flows up the annular space between adjacent casing strings. In cementing operations carried out in 'wells drilled on land, the casing suspension body or casinghead is usually provided with a side outlet immediately below the casing hanger seat so that fluid within the well can be displaced out of the annular space outside the well casing while the casing hanger rests on its seat. In the event that no side outlet is provided in the casinghead or casing suspension body, fluid in the annular space outside the casing can only be circulated out of the well by holding the casing hanger off its seat in the casingr head so as to allow fluid to circulate past. In most cases, the casing hanger is not installed until after cementing operations have been completed. In cementing operations on land this operation is accomplished by employing a derrick with suitable hoist means for coupling to the top of the string of well casing and supporting it in a manner such that its hanger is suspended just above the casing suspension bowl or the casing hanger seat.

With cementing operations being carried out from a floating vessel, the vessel from which operations are carried out rises and falls vertically as wave trains pass the vessel, which precludes suspending the weight of the casing string from a derrick on the vessel, as the casing string would necessarily rise and fall with the vessel. The amount of vertical travel of the casing string and vessel, which would be a function of the period and wave heights of the particular waves passing the vessel, may often be of suflicient magnitude so that the hanger, fixedly secured to the suspended casing, would bump its seat within the casing suspension body or casinghead as the vessel moved and its seat not only tends to damage the hanger and/or its seat, but also tends to cause pressure fluctuation within the well which increases the possibility of losing circulation during the cementing operation.

It is therefore a primary object of the present invention to provide a method and apparatus for carrying out ce-' menting operations from a floating vessel when it is desired to cement well casing in an underwater well where it is necessary to suspend fixedly the Well casing temporarily above its sealed position.

Another object of the present invention is to provide a method and apparatus to carry out well casing cementing operations from a floating vessel when it is desired to cement well casing in an underwater well while the vessel is free to move vertically with regard to the well casing and any associated cementing pipe string employed in the cementing operations.

A further object of the present invention is to provide a method and apparatus for carrying out cementing operations from a floating vessel when it is desired to cement well casing in an underwater wellhead assembly which is not provided with side outlets through which fluid may be discharged during cementing operations.

Another object of the present invention is to provide apparatus adapted to be connected bet-ween the bottom of a pipe string and the top of a casing string for temporarily hanging a casing hanger off its seat during the circulation of cement to its predetermined position outside the casing string.

It is a further object of the present invention to provide a method and apparatus for carrying out cementing operations from a floating vessel at offshore wells positioned underwater so that any fluid in the well can be displaced out of the top of the well during cementing operations.

These and other objects of this invention will be understood from the following description taken with reference to the drawing, wherein:

FIGURE 1 is a schematic view illustrating the operation of positioning a well casing and associated equipment within a well drilled in the ocean floor, said operations being carried out from a floating vessel on the surface of the water;

FIGURE 2 is a view, taken in partial cross-section, of a mechanically-operated temporary well casing support means as employed in the equipment of FIGURE 1;

FIGURE 3 is a view taken in longitudinal cross-section of a hydraulically-operated temporary casing support to be used with the equipment illustrated in FIGURE 1;

FIGURE 4 is a view taken in longitudinal cross-section of another type of easing suspension equipment which may be employed to carry out the method of the present invention; and,

FIGURE 5 is an enlarged detailed view, taken in longitudinal cross-section, of a threaded portion of the apparatus of FIGURE 1.

Referring to FIGURE 1 of the drawing, a drilling barge 11 of any suitable floatable type is illustrated as floating on the surface of the water 12 and being fixedly positioned over a preselected drilling location by being anchored to the ocean floor 13 by anchors (not shown) at the end of the cables 14 and 15-. Equipment of this type may be used when carrying on well-drilling operations in water varying from about feet to about 1500 feet ormore. The drilling barge 11 is equipped with -a suitable derrick 16 which in turn is provided with a hoist 17, fall lines, rotary table, as well as other auxiliary equipment (not shown) needed during the drilling and completion of a well. The derrick 16 ispositioned over a drilling slot or well 18 which extends vertically through the barge in a conventional manner. When using the equipment of the present invention the slot 18 in the barge 11 may be either centrally located or extend in from one edge.

I 3 However, drilling operations may be carried out over the side of the barge without use of a slot.

While prior to actual drilling operations a wellhead support structure may have been positioned on the ocean floor, for ease of illustration and description the present invention will be described with regard to a casinghead 21 which is fixedly secured to a base plate 22. The lower end of the oasinghead 21 extends downwardly a distance sufiicient so that the top of a conductor pipe 23 can be fixedly secured thereto in any suitable manner, as by screw threads or welding. The wellhead assembly or casinghead 21 may be positioned in place during well drilling operations which may be carried out in a manner described in .copending application, Serial No. 830,538, filed July 30, 1959, and entitled Underwater Well Completion Method. In accordance with the method described in the above-identified patent application, a marine conductor 24 is assembled and lowered from the floating vessel 11 until its lower end is aligned and seated in the top of the casinghead 211 or suitable equipment mounted on the top thereof. The marine conductor 24 is preferably positioned within the slot 18 of the vessel 11 but is retained therein in a manner such that the vessel 11 is able to move vertically independently of the marine conductor 24. Positioned within the marine conductor 24 is a pipe string 25 through which cement may be pumped, and hence is normally called a cementing string. The top of the cementing string 25, which is positioned adjacent the vessel 11 above the surface of the water 12, may be connected by means of a hose or pipe to a suitable pump (not shown) for pumping a cement slurry down through the pipe string 25.

Fixedly mounted on the bottom of the pipe string 25 is a temporary casing support device 26, one type of which is shown in greater detail in FIGURE 2. The temporary casing support device 26 may take any of several forms and may be actuated in any suitable manner, as by the rotation of pipe string 25 or through the application of a pressure fluid through the pipe string 25'. The particular temporary casing support device 26 shown in FlGURE 2 comprises a housing 27 having two or more landing dogs 28 and 29 mounted for sliding lateral or radial movements in a pair of landing dog slots 32 and 33. A slip bowl 34 of any conventional type is formed within the housing 27 with two or more slip elements 35 and 36 mounted for sliding movement in the bowl 34 in a manner such that the outer faces of the slip elements 35 and 36 urge the landing dogs 28 and 29 outwardly as the slips 35 and 36 are forced downwardly. The slip elements '35 and 36 are forced downwardly against spring 4% by means of a pressure plate or other element which is rigidly secured against vertical movement on a lead screw 38 which passes through the threaded portion 39' at the top of the housing 27. The top of the lead screw is secured to the bottom of the pipe string 25 so that upon rotation of the pipe string from the surface the pressure plate 37 within the housing will either be raised or lowered thus setting the slip elements '35 and 36 or permitting them to be released. The landing dogs 28 and 29 are preferably arranged to be held in a retracted position by means of compression springs 42 mounted within a slot 43 in the housing 27 and bearing against a pin 44' rigidly afiixed to the landing dog 28 and slidably mounted within the slot 43.

The landing dogs 28 and 29' of the temporary easing support device are adapted to move outwardly a distance sufficient to engage a temporary casing support seating device which may take the form of individual elements 45 and 46 fixedly secured to the inner wall of the marine conductor 24 preferably near the bottom thereof. Al ternatively, the temporary casing support seating device may take the form of a continuous shoulder 47 fixedly secured to the inner wall of the marine conductor 24- instead of the elements 45 and 46. Also, as illustrated, instead of the seating shoulder 47 being in the lower 4 end of the marine conductor 24, it may be positioned in the upper end of the casinghead 21.

Regardless of the element to which the temporary casing support seating device is attached, it must be positioned a known fixed distance above the casing suspension bowl or casing hanger seat 50 from which a string of casing 51 is to be hung. In order to hang the casing, the top of the casing 51 is provided with any conventional type of casing hanger 5-2 which may be provided with any suitable type of seals 53 and is adapted to be seated in the casing suspension bowl 50. Although for ease in illustration a simple casing hanger 52 is illustrated as being threaded to the top of the casing string 51, it is realized that any type of casing hanger may be employed, for example, one having hold-down slips, etc., and may be connected to the top of the well casing in any other suitable manner, as by welding.

Threadedly connected to the bottom of the lead screw 38, which extends through the bottom of the temporary casing support device 26 and fixedly secured thereto, is a spacer tube 54 which has a suitable connector element 55 aflixed to the lower end thereof which is adapted to engage, as by screw threads 56, the top of the casing hanger 52. The length of the spacer tube 54 is critical and should be of a length such that when the temporary casing support device 26 is positioned on its seating elements 45 and 46, the casing hanger 52 remains a predetermined distance off the casing suspension bowl 50, say, anywhere from about two inches to two feet or more so that an annular passageway 57 is provided between the casing hanger 52 and the bowl 50 whereby fluid in the annular passageway 60 between the casing string 51 and the conductor pipe 23 may be forced upwardly past the seating bowl 50 during cementing operations. If desired, in some installations the connector 55 may be secured against rotation in the threaded top of the casing hanger 52 by means of a low-strength shear pin 61. While the connector 55 at the bottom of the spacer tube 54 has been shown, for ease in illustrating, as a screw-threaded connection, it is realized that any suitable connection may be employed between the bottom of the spacer tube and the top of the hanger, such for example as a J-slot connector or other types well known to the art of oil well drilling.

If desired, the bottom of the spacer tube 54, which is actually the bottom of the cementing string 25, may have an extension secured to it known as a cementing stinger 62. The cementing stinger is preferably provided with one or more cementing plugs such as a wiper plug 63 and a follower plug 64 which are preferably secured to the bottom of the cementing stinger 62 by means of shear pins. These elements are well known to the art of oil well cementing and since they do not form a novel part of the present invention they will not be further described or illustrated here.

In the operation of the method of the present invention, a string of well casing is lowered from a floating vessel 11 (FIGURE 1) into the casinghead 21 and down into the well. When the desired length of casing has been inserted into the well, the casing hanger 52 is fixedly secured to the top of the casing on the barge and then the connector 55, spacer tube 54 and temporary casing support device 26 are successively mounted one on top of each other above the top of the casing string hanger 52. Lastly, the cementing string 25 is connected to the top of the temporary casing support device 26 and the entire string of pipe and casing is lowered into the well, preferably through a marine conductor, as illustrated. If desired, the landing dogs 28 and 29 of the temporary casing support device 26 may have been previously set in their outermost position so that upon contact with the seating elements 45 and 46 at the bottom of a marine conductor 24, or with the seating shoulder 47 within the casinghead 21, the entire string of pipe and casing will he landed in the manner illustrated with the casing hanger 52 being positioned a fixed distance above the casing suspension bowl 50 so that an annular space 57 is formed through which the fluid can be circulated or displaced. In this described position, the casing and pipe string are fixedly positioned on the wellhead assembly and are unaffected by any vertical movement of the vessel due to wave action.

Cementing operations are then carried out in a normal manner well known to the art with a hose or pipe (not shown) being connected to the top of the cementing string 25 and a quantity of cement being pumped down the cementing string 25. As the cement flows out of the bottom of the cementing string it will push the wiper plug 63 ahead of it. The wiper plug 63 in turn forces any fluid within the well casing 51 down to the bottom of the well casing and subsequently up'the annular space 60 between the well casing 51 and the conductor pipe 23, thence outwardly through the annular space 57 between the seat 50 and the casing hanger 52 and finally up past the temporary casing support device 26 and up the annular space between the cementing string 25 and the inner wall of the marine conductor 24, if the marine conductor is employed. After circulating a predetermined amount of cement down into the cementing string 25, a ball may be dropped down which blocks the passage through the follower plug 64 causing a following fluid to shear the pin holding plug 64 to the bottom of the cement stinger. The follower plug 64 is pumped down through the well casing with water behind it until it reaches the bottom of the casing at which time all of the cement will have been forced up the annular space between the casing string and the side of the borehole or the inner wall of the next most outwardly casing string. At this time, before the cement sets up in the well, the cementing string 25 is rotated in a manner such that the slip elements 35 and 36 (FIGURE 2) move upwardly in the slip bowl 34, causing the landing dogs 28 and 29 to be retracted by compression springs 42 so that the entire string of cementing pipe and well casing may be lowered slightly so that the casing hanger 52 seats itself in the casing suspension bowl 50. If necessary, the cementing string may be picked up during rotation so that the landing dogs are retracted more easily. At this time continued rotation of the cementing string releases the connector 55 from the top of the casing hanger 52 and the connector 55, spacer tube 54, temporary casing support device 26 and the cementing string 25, are all then withdrawn upwardly to the vessel 11 at the surface.

Instead of the temporary casing support device 26 of FIGURE 1 being of the type that is actuated by rotation of the cementing string 25, a casing support device of the type illustrated in FIGURE 3 may beemployed. In this figure, the casing support device is shown as being seated on a shoulder 47 within the casinghead 21 although it is to be understood that it could also be seated on a shoulder at the bottom of a marine conductor, as illustrated in FIGURE 1, or on any element in between a marine conductor and a casinghead. The hydraulicallyoperated temporary casing support device illustrated in FIGURE 3 comprises a tubular body or housing 65 having two or more landing dogs 66 pivotally mounted thereon, as by a pin 67, with a compression spring 68 acting against the arm of the landing dog 66 to retain it in a normally inoperative position against the housing 65. Sildaoly mounted on the outside of the housing 65, just above the dogs 66, is a circular dog-holding piston 71 provided with a compression spring 72 thereabove for normally urging the dog-holding piston 71 downwardly in back of the landing dogs 66. O-ring seals 73 and 74 may be provided between the dog-holding piston 71 and the outer wall of the housing 65 so as to prevent the escape of pressure fluid applied through a pressure port 75 through the wall of the housing 65'.

In employing the form of the apparatus shown in FIG- URE 3, the landing dogs 66 would be set in their outermost position, as illustrated, prior to running the cement ing string and the temporary casing landing device to its seating position on the shoulder 47 of the casinghead 21. After cementing operations have been carried out in a manner described with regard to FIGURE 1, the hoist on the vessel 11 would be employed to pick up the entire cementing pipe string to take the weight off of the landing dog 66 temporarily. A pressure fluid applied through the cementing string and the housing passes outwardly through the pressure port and acts against the dogholding piston 71 to force it upwardly against the retaining spring 72. When the bottom of the dog-holding piston 71 is above the top of the landing dogs 66, the springs 68 force the dogs 66 into their inoperative position against the outer wall of the housing 65. If desired, the bottom of the dog-holding piston may be provided with a retaining notch or groove 76 and the top of the landing dog 66 may be provided with a retaining peg 77 for holding the landing dog 66 against the outer face of the housing 65 when the pressure Within the cementing string 25 is released.

Another form of the apparatus of the present invention is shown in FIGURE 4 of the drawing with a detail of a portion of FIGURE 4 being enlarged in FIGURE 5. The apparatus, which may be substituted for that shown in FIGURE 1, comprises an inner sleeve 101 connected to the bottom of a cementing string 117, an outer sleeve 102 forming a part of the spacer tube 104, a suspension plug 103 having a downwardly extending sleeve 124, and a hanger adaptor 105 connected to a casing hanger by means of landing threads 111. The apparatus is designed to operate in combination with a marine conductor 24 or casinghead 21 of FIGURE 1, shown in FIGURE 4 as element 106, and being provided with an upwardly facing shoulder 108 adapted to receive the downwardly facing shoulder 107 of the suspension plug 103 so that the weight of the casing string 109 is transferred to the casing suspension body 106, whether it be a marine conductor or a casinghead. The casing string weight is transferred through the casing hanger 110, the landing threads 11 1 on the hanger adaptor 105, to the spacer tube 104. The translatory threads 112 on the outer sleeve 102 transfer the weight to the threads on the inner sleeve 101. From the inner sleeve the weight is transferred to the suspension plug 103 through thrust-bearing 114 and then to the shoulder 108 of the casing suspension body 106. The suspension plug 103 is equipped with splines 116 which fit into grooves along the vertical face of shoulder 108. When the splines are engaged in the grooves it is not possible for the suspension plug 103 to rotate with respect to the suspension body 106. In FIGURE 4, the apparatus is shown when the casing weight is suspended from the suspension body 106, as it would be prior to cementing of the casing string. While in this position, cement can be pumped down the cementing string 117 through the tool and the casing string 10 9 to return up the well, in a manner described with regard to FIGURE 1, through the annular space between the casing hanger 110 and the casing hanger seat 118, and thence upwardly through ports 119 provided in the suspension plug 103.

After the cement has been displaced to its desired position, the cementing string 117 is rotated to the right, however it is to be understood that the tool could be designed with left-hand rotation at this point. Since the outer sleeve 102 is locked to the suspension plug 103 by keys 120 which are connected to the outer sleeve and ride in the key slots 121, the slots 121, being parts of the downwardly extending sleeve 124 of the suspension plug 103, prevent the outer sleeve 102 from rotating so that the translatory threads 112 are fed off the corresponding threads on the inner sleeve 101 as the latter rotates within 'the outer sleeve 102. The feeding off of the translatory threads 112 causes the spacer tube 104, the casing hanger 110 and the casing string 109 to be lowered with respect to the casing hanger seat 118 and eventually causes the casing hanger 110 to rest in the casing hanger seat 118.

After the casing hanger "110 has been seated, continued rotation of the cementing string 117 causes the suspension plug 103 to move upward and retract the splines 116 from the grooves in the vertical face of the seating shoulder 108 of the suspension body 106. When the splines 116 have been completely retracted the suspension .plug 103 is free to rotate. As the cementing string 117 continues to be rotated to the right, the locking threads 122 at the upper end of the outer sleeve 102 mesh with the stop threads 123 on the inner sleeve 101. At the time that these threads are completely meshed, the keys 120 are completely withdrawn from the key slots 121 in the suspension plug 103, and rotation of the cementing string 117 thereafter causes a rotation of the spacer tube 104. The rotation of the spacer tube 104 backs the hanger adaptor 105 out of the landing threads 111 in the casing hanger 110 and releases the spacer tube 104 so that the spacer tube together with the suspension plug 103 can be retrieved from the well by raising the cementing string 117 to the surface.

We claim as our invention:

1. In well drilling operations carried out from a floating structure, a method of cementing casing in a fluidfilled well at an offshore location which comprises drilling a well in the ocean floor, installing in said well a wellhead assembly adapted to seat a casing therein, lowering into said well from said floating structure a well casing having hanger means thereon and being connected to the lower end of a pipe string, rigidly supporting temporarily the hanger means a fixed distance above the seat in said wellhead assembly to form a fluid passageway between said seat and hanger means, circulating a quantity of cement slurry down said pipe string and well casing whereby fluid filling the well is forced upwardly outside said well casing and through said fluid passageway between said seat and hanger means, pumping a quantity of fluid down said pipe string and well casing in back of said cement to force the cement up the outside of said well casing, subsequently lowering the well casing to seat the hanger means thereof in a fluid-tight manner within said wellhead assembly before the cement starts to set, disconnecting said pipe string from said well casing and Withdrawing it to a point above the surface of the water.

2. In well drilling operations carried out from a floating structure, a method of cementing casing in a fluidiilled well at an ofishore location which comprises drilling a well in the ocean floor, installing in said well a wellhead assembly adapted to seat a casing therein, positioning a marine conductor pipe on the top of said welihead assembly to extend from the top thereof to a point above the surface of the water, lowering through said marine conductor pipe and into said well from said floating structure a well casing having hanger means thereon and being connected to the lower end of a pipe string, rigidly supporting temporarily said well casing with its hanger means, a fixed distance above the seat in said wellhead assembly to form a fluid? passageway between said seat and hanger means, circulating a quantity of cement slurry down said pipe string and well casing whereby fluid filling the well is forced upwardly outside said well casing and through said fluid passageway between said seat and hanger means, pumping a quantity of fluid down said pipe string and well casing in back of -said cement to force the cement up the outside of said well casing, subsequently lowering the well casing to seat the hanger means thereof in a fluidtight manner within said wellhead assembly before the cement starts to set, disconnecting said pipe string from said well casing and withdrawing it to a point above the surface of the water.

3. In well drilling operations carried out from a floating structure, a method of cementing casing in a fluidfilled well at an offshore location which comprises drilling a well in the ocean floor, installing in said well a wellhead assembly adapted to seat a casing therein, positioning a marine conductor pipe on the top of said wellhead assembly to extend from the top thereof to a point above the surface of the water, lowering through said marine conductor pipe and into said well from said floating structure a Well casing having hanger means thereon and being connected to the lower end of a pipe string, rigidly supporting temporarily said well casing with its hanger means a fixed distance above the seat in said wellhead assembly to form a fluid passageway between said seat and hanger means, said hanger means and well casing being supported from said marine conductor pipe, circulating a quantity of cement slurry down said pipe string and well casing whereby fluid filling the well is forced upwardly outside said well casing and through said fluid passageway between said seat and hanger means, pumping a quantity of fluid down said pipe string and well casing in back of said cement to force the cement up the outside of said well casing, raising said well casing a short distance to disengage said temporary rigid support, subsequently lowering the well casing to seat the hanger means thereof in a fluidtight manner within said wellhead assembly before the cement starts to set, discon necting said pipe string from said well casing and withdrawing it to a point above the surface of the water.

4. Apparatus for cementing well casing in a fluid-filled well from a floating vessel at an offshore location, said apparatus comprising well casing suspension body means fixedly positioned in the top of a well drilled in the ocean floor and extending upwardly therefrom, a casing suspension means carried within said suspension body means, temporary casing-support seating means carried within said suspension body means above said casing suspension means in spaced relationship therewith, a floating vessel on the surface of the water positioned over said suspension body means, a cementing pipe string extending from a point adjacent said vessel down into said suspension body means, said vessel being positioned for free rise and fall movement with respect to said pipe string during cementing operations, temporary casing support means connected to the lower end of said pipe string, a spacer tube connected to the lower end of said casing support means coaxial with said pipe string, connector means carried on the lowe end of said spacer tube for detachably connecting a casing hanger thereto, a casing hanger detachably connected to said connector means and adapted to seat within said casing suspension means, the distance between the temporary casing support means and said casing hanger being at least slightly less than the distance between said temporary casing support seating means and said casing suspension means, and a string of easing having its upper end fixedly secured to said casing hanger.

5. Apparatus for cementing well casing in a fluid-filled well from a floating vessel at an offshore location, said apparatus comprising well casing suspension body means fixedly positioned in the top of a well drilled in the ocean floor and extending upwardly therefrom, a casing suspension bowl formed within said suspension body means, temporary casing support seating means carried within said suspension body above said casing suspension bowl in spaced relationship therewith, a floating vessel on the surface of the water anchored over said suspension body means, a cementing pipe string extending from a point adjacent said vessel down into said suspension body means, said vessel being positioned for free rise and fall movement with respect to said pipe string during cementing operations, temporary casing support means connected to the lower end of said pipe string, said temporary casing support means including radially extensible and retractable landing dogs and means for retracting said landing dogs upon rotation of said pipe string from the vessel, a spacer tube connected to the lower end of said temporary casing support means coaxial with said pipe string, connector means carried on the lower end of said spacer tube for detachably connecting a casing hanger thereto, an annular casing hanger detachably connected to said connector means and adapted to seat within said casing suspension bowl, the distance between the temporary casing support means and said casing hanger being at least slightly less than the distance between said temporary casing support seating means and said casing suspension bowl, and a string of easing having its upper end fixedly secured to said casing hanger.

6. Apparatus for cementing well casing in a fluid-filled well from a floating vessel at an ofishore location, said apparatus comprising well casing suspension body means fixedly positioned in the top of a well drilled in the ocean floor and extending upwardly therefrom, a casing suspension bowl formed within said suspension body means, temporary casing support seating means carried within said suspension body above said casing suspension bowl in spaced relationship therewith, a floating vessel on the surface of the water anchored over said suspension body means, a cementing pipe string extending from a point adjacent said vessel down into said suspension body means, said vessel being positioned for free rise and fall movement with respect to said pipe string during cementing operations, temporary casing support means connected to the lower end of said pipe string, said temporary casing support means including radially extensible and retractable spring-loaded landing dogs, and spring means and piston means for retracting said landing dogs upon application of pressure fluid through said pipe string after cementing operations have been completed, port means in said temporary casing support means in communication between said piston means and the interior of said pipe string, a spacer tube connected to the lower end of said casing support means coaxial with said pipe string, connector means carried on the lower end of said spacer tube for detachably connecting a casing hanger thereto, an annular casing hanger detachably connected to said connector means and adapted to seat within said casing suspension bowl, the distance between the temporary casing support means and said casing hanger being at least slightly less than the distance between said temporary casing support seating means and said casing suspension bowl, and a string of casing having its upper end fixedly secured to said casing hanger.

7. Apparatus for cementing well casing in a fluid-filled Well from a floating vessel at an offshore location, said apparatus comprising a well casinghead fixedly positioned on the ocean floor and extending upwardly therefrom, a casing suspension bowl formed within said casinghead, an elongated marine conductor pipe detachably connected to the top of said casinghead and extending upwardly to above the surface of the water, temporary casing support seating means carried within said marine conductor pipe, a floating vessel on the surface of the water positioned over said casing head and adjacent said conductor pipe, a cementing pipe string extending down through said conductor pipe, said vessel being positioned for free rise and fall movement with respect to said conductor pipe and said pipe string, temporary casing support means connected to the lower end of said pipe string, a spacer tube connected to the lower end of said temporary casing support means coaxial with said pipe string, connector means carried on the lower end of said spacer tube for detachably connecting a casing hanger thereto, an annular casing hanger detachably connected to said connector means and adapted to seat within said casing suspension bowl, the distance between the temporary casing support means and said casing hanger being at least slightly less than the distance between said temporary casing support seating means and said casing suspension bowl, and a string of easing having its upper end fixedly secured to said casing hanger.

8. Apparatus for cementing well casing in a fluid-filled well from a floating vessel at an offshore location, said apparatus comprising well casing suspension body means fixedly positioned in the top of a well drilled in the ocean floor and extending upwardly therefrom, a casing suspension bowl formed within said suspension body means, temporary casing support seating means carried within said suspension body above said casing suspension bowl in spaced relationship therewith, a floating vessel on the surface of the water anchored over said suspension body means, a cementing pipe string extending from a point adjacent said vessel down into said suspension body, said vessel being positioned for free rise and fall movement with respect to said pipe string during cementing operations, temporary casing support means connected to the lower end of said pipe string, a spacer tube connected to the lower end of said temporary casing support means coaxial with said pipe string, connector means carried on the lower end of said spacer tube for detachably connecting a casing hanger thereto, an annular casing hanger detacha-bly connected to said connector means and adapted to seat within said casing suspension bowl, the distance between the temporary casing support means and said casing hanger being at least slightly less than the distance between said temporary casing support seating means and said casing suspension bowl, a string of casing having its upper end fixedly secured to said casing hanger, and screw-thread means carried by said casing support means for extending said spacer tube to seat said casing hanger on said casing suspension bowl upon rotation of said pipe string from said vessel.

9. Apparatus for cementing well casing in a fluid-filled well from a floating vessel at an olfshore location, said apparatus comprising a well casinghead fixedly positioned in the top of a well drilled in the ocean floor and extending upwardly therefrom, a casing suspension bowl formed within said casinghead, an elongated marine conductor pipe detachably connected to the top of said casinghead and extending upwardly to above the surface of the water, temporary casing support seating means carried within said casinghead above said casing suspension bowl in spaced relationship therewith, a floating vessel on the surface of the water anchored over said casinghead and adjacent said conductor pipe, a cementing pipe string extending down through said conductor pipe and into said casinghead, said vessel being positioned for free rise and fall movement with respect to said conductor pipe and said pipe string, temporary casing support means connected to the lower end of said pipe string, a spacer tube connected to the lower end of said temporary casing support means coaxial with said pipe string, connector means carried on the lower end of said spacer tube for detachably connecting a casing hanger thereto, an annular casing hanger detachably connected to said connector means and adapted to seat within said casing suspension bowl, the distance between the temporary casing support means and said casing hanger being at least slightly less than the distance between said temporary casing support seating means and said casing suspension bowl, a string of easing having its upper end fixedly secured to said casing hanger, and a cementing stinger extending concentrically within said casing string with its upper end fixedly secured to said connector means in communication with the lower end of said pipe string.

References Cited in the file of this patent UNITED STATES PATENTS 2,891,770 Bauer et a1. June 23, 1959 2,909,359 Bauer et al. Oct. 20, 1959 2,917,281 Kofahl Dec. 15, 1959 2,929,610 Stratton Mar. 22, 1960 FOREIGN PATENTS 814,520 Great Britain June 3, 1959 

